In cultivating farmland, obstructions are often encountered in the soil by the ground working tool and, in the absence of some device to reduce the impact of the obstruction with the ground working tool or to allow the ground working tool to give way to the obstruction, the tool can be damaged or destroyed which can be costly and time consuming to replace. In respect to blade cultivators which are used for minimum tillage farming, the replacement cost is particularly high due to the size and quality of the blade.
Previous efforts to solve the problem have not been satisfactory. Perhaps the most rudimentary effort to prevent blade or ground working tool damage is by providing a simple shear bolt to take the force of the impact of the tool with the obstruction. While this prevents destruction of the blade or ground working tool, it does not prevent destruction of the bolt and down time is necessitated by the bolt replacement. A further adverse feature is that if the bolt is sheared, the tillage tool or blade will deflect in a position transverse to the ground called "tip up" thereby "digging a hole" with the tip of the blade. Unless the "hole" is again passed over by the cultivator and filled in, damage or delay to machinery such as swathers or windrowers, which subsequently pass over the hole, can result. Thus, an additional pass needs to be made over the "hole" which requires additional field time.
Another adverse feature following from this "tip up" type of deflection mechanism, particularly with blade type cultivators, is that adequate clearance must be maintained between the blade and the implement frame to allow for the "tip-up". Providing this required clearance is, in many instances, undesirable because of transportation and other space limitations.
A further disadvantage associated with previous type mechanisms is that "detents" are not incorporated into the design. Detents retain a trip mechanism in its working position until a certain force is reached whereas the detent trips and allows deflection of the working tool. Adjustment of the trip mechanism is facilitated by an easily adjustable detent which will not allow the mechanism to trip until the predetermined force is reached.
A requirement of trip mechanisms, particularly when used wth blade type cultivators, is that it needs to be heavy and rugged to withstand the larger forces generated when obstructions are encountered. Previous trip mechanisms tend to be light duty and unsuitable for heavier duty blade cultivator applications.